The invention relates to a method for determining the wear to an electrochemical energy store resulting from the loss of storage capacity, and to an energy store, in particular a starter battery for motor vehicles, having measurement means for determining the amounts of charge converted during the charging cycles of the energy store, and having computation means.
Energy stores, for example rechargeable electrochemical storage batteries, are subject to wear, in particular during discharging and charging. In addition to discharging and charging, there are also other operating conditions which speed up the wear to electrochemical energy stores. These include, for example, the total operating life in the case of a lead-acid rechargeable battery, that is to say the total time which has passed since it was brought into use, including the periods in which the rechargeable battery had no electrical load applied to it.
Furthermore, increased temperatures can increase the wear during periods without any electrical load being applied, and the wear caused by cyclic discharging and charging.
For the use of energy stores, it is desirable to determine the wear on the basis of the loss of storage capacity. However, the complexity of the processes that take place in the energy store represent a problem in this case, which can be described only with difficulty by using scientific methods.
By way of example, DE 195 40 827 C2 discloses an empirical method for determining the aging state of a battery, in which a battery-specific family of characteristics is predetermined for battery aging. A battery aging value is determined with the aid of the family of characteristics by recording instantaneous values of battery aging influencing variables for the battery that is being monitored.
DE 39 01 680 C3 discloses a method for monitoring the cold starting capability of a starter battery in which, when the internal combustion engine is running, the charging voltage is observed continuously and is monitored to determine whether it has exceeded or fallen below predetermined limit values. This makes it possible to identify a defect in the generator. Furthermore, the time profile of the voltage drop across the connecting terminals of the electrical starter is observed and evaluated during the starting process. However, in this case, it is not possible to make any statement about the available storage capacity of the energy store.
DE 38 08 559 C2 discloses a method for monitoring the power limit of a starter battery, in which an amount of charge balance is produced by adding up the amounts of charge which have flowed in and flowed out. The state of charge of the starter battery is assessed from this, in conjunction with the monitoring of a limiting terminal voltage and the temperature. It is not possible to make any statement about the remaining maximum storage capacity of the energy store in this case, either.
The object of the invention was thus to provide a method for determining the wear to an electrochemical energy store resulting from the loss of storage capacity, by means of which a wear variable can be calculated reliably and using simple means, as a measure of the loss of storage capacity.